In this proposal, the Department of Chemistry at Colorado State University requests funds to purchase a new single crystal X-ray diffraction system. The system chosen will enhance significantly the department's ability to supply both routine and specialty X-ray structural results for the research programs of a group of seven major users with biomedical research interests and current NIH funding. An additional group of five major users, representing a broad spectrum of other research interests within the department, will also benefit from the proposed X-ray diffraction instrumentation. The new diffraction system will be able to provide extremely rapid, high-precision data collection for normal crystals. An objective of the new facility will be to provide one-day turnaround (or less) for routine structure determinations on compounds of biomedical interest and importance. The new facility will also be capable of providing high quality X-ray diffraction data from weakly diffracting or highly absorbing crystals that do not yield satisfactory data with the existing X-ray diffraction instrumentation. The new system will include low-temperature data acquisition capability, in order to allow high-quality low-temperature data to be collected routinely on all samples. Overall, this instrumentation will bring modern, high-speed single crystal X-ray structure determination capabilities to bear on a wide range of biomedically-related research in chemistry at Colorado State University. It is expected to dramatically enhance the progress of that research, thus improving the quality of the investment (almost $ 1.3 M this year) that the National Institutes of Health is currently making in biomedically-related research in the Department of Chemistry at Colorado State University.